If you send money to the wrong person and they don't give it back, you can try sue them to give it back, but there is no inherent law that they must do so.
Or am I wrongly informed? Because that's the knowledge I have from central european laws.
> Wer durch die Leistung eines anderen oder in sonstiger Weise auf dessen Kosten etwas ohne rechtlichen Grund erlangt, ist ihm zur Herausgabe verpflichtet. Diese Verpflichtung besteht auch dann, wenn der rechtliche Grund später wegfällt oder der mit einer Leistung nach dem Inhalt des Rechtsgeschäfts bezweckte Erfolg nicht eintritt.
> A person who obtains something as a result of the performance of another person or otherwise at his expense without legal grounds for doing so is under a duty to make restitution to him. This duty also exists if the legal grounds later lapse or if the result intended to be achieved by those efforts in accordance with the contents of the legal transaction does not occur.
Basically there is law that says for every money send should be a cause, reason that justifies sending. If there is no such reason, reciever is entitled to send them back.
Or am I wrongly informed? Because that's the knowledge I have from central european laws.